Fair Value Measurements and Derivative Instruments (Tables)

6 Months Ended

Mar. 31, 2024

Derivative Instruments Gain Loss [Line Items]

Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

The following tables summarize the financial assets and liabilities measured at fair value on a recurring basis as of March 31, 2024 and September 30, 2023:

	March 31, 2024
	Carrying Value		Level 1		Level 2		Level 3
Other current assets:
Fuel derivative contracts		0.1		—		0.1		—
Other assets:
Investments held by Rabbi Trust	$	11.9	$	11.9	$	—	$	—
Interest rate derivative contracts		12.4		—		12.4		—
Total assets	$	24.4	$	11.9	$	12.5	$	—
Other liabilities:
Obligation to Rabbi Trust	$	11.9	$	11.9	$	—	$	—
Total liabilities	$	11.9	$	11.9	$	—	$	—

	September 30, 2023
	Carrying Value		Level 1		Level 2		Level 3
Other assets:
Investments held by Rabbi Trust	$	10.9	$	10.9	$	—	$	—
Interest rate derivative contracts		21.3		—		21.3		—
Total Assets	$	32.2	$	10.9	$	21.3	$	—
Other liabilities:
Obligation to Rabbi Trust	$	10.9	$	10.9	$	—	$	—
Total Liabilities	$	10.9	$	10.9	$	—	$	—

Interest Rate Contracts

Derivative Instruments Gain Loss [Line Items]

Summary of Effects on Consolidated Financial Statements of Designated As Cash Flow Hedges

The effects on the consolidated financial statements of the interest rate contracts which were designated as cash flow hedges were as follows:

	Three Months Ended March 31,				Six Months Ended March 31,
	2024		2023		2024			2023
Income (Loss) recognized in Other comprehensive income (loss)	$	10.9	$	1.5	$	(3.6	)	$	1.5
Net income reclassified from Accumulated other comprehensive income into Interest expense		2.8		1.3		5.6			4.3

Fuel Swap Contracts

Derivative Instruments Gain Loss [Line Items]

Summary of Effects on Consolidated Financial Statements of Designated As Cash Flow Hedges

The effects on the consolidated financial statements of the fuel swap contracts which were designated as cash flow hedges were as follows:

	Three Months Ended March 31,				Six Months Ended March 31,
	2024		2023		2024		2023
Income recognized in Other comprehensive income (loss)	$	0.1	$	—	$	0.1	$	—
Net gain reclassified from Accumulated other comprehensive income into Cost of services provided		—		—		—		—